1. Field of the Invention
The present invention relates to turbines and gas turbines.
2. Description of the Related Art
U.S. Pat. Nos. 5,385,446 and 5,624,235 disclose steam turbines and U.S. Pat. Nos. 5,611,197 and 5,791,136 disclose gas turbines. In these conventional turbines and gas turbines, turbines are usually composed of multi-stage stator vanes and multi-stage turbine blades. Each of turbine blades normally has a convex outer surface and a concave inner surface upon which motive gases impinge to produce a positive torque. In this instance, since the outer surface of each blade impinges upon the motive gases axially flowing through the turbine, a reactive force (i.e., a negative torque) is produced in a rotational direction of the turbine blades and, thus, an output shaft has an output power which is a result of the positive and negative torques. In these turbine structures, further, since the turbine rotor rotates at an extremely high speed, the motive gases tend to rotate with the turbine blades in a unitary fashion so that a huge centrifugal force and a fluidic wall are produced in a space between a turbine housing and the turbine rotor. Under these circumstances, the motive gases can not readily flow in the axial direction, thereby reducing the turbine efficiency. For this reason, the turbine and the gas turbine become large in structure, thereby increasing the manufacturing costs, while increasing the operation noises.